Portable computer with low-power audio CD-player

ABSTRACT

A system and method to reduce power consumption in a portable computer system while allowing the CDROM drive to continue playing audio CDs. When the system enters a suspend mode, the status of the CDROM drive is checked, and if it is playing an audio CD, it remains powered, otherwise power to the CDROM drive, is also suspended. The system recognizes when the audio CD is finished playing and then places the CDROM drive into the suspend mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 09/801,386, filed Mar. 8,2001, which is a continuation of 09/566,748, filed May 9, 2000 (now U.S.Pat. No. 6,378,077, issued Apr. 23, 2002), which is a continuation of09/150,530, filed Sept. 10, 1998 (now U.S. Pat. No. 6,088,809, issuedJul. 11, 2000), which is a continuation of 08/699,989, filed Aug. 20,1996 (now U.S. Pat. No. 5,838,983, issued Nov. 17, 1998) and also claimspriority from provisional 60/019,109, filed Jun 3, 1996, all of whichare hereby incorporated by reference. However, the content of thepresent application is not necessarily identical to that of the priorityapplication.

BACKGROUND AND SUMMARY OF THE INVENTION

Multimedia PCs often incorporate CD-ROM drives and audio subsections.CD-ROM players are valuable as data storage devices, but also may beused to play standard Audio CD disks. However, typical computers todayrequire that the CPU be fully “on” to play an audio CD. As a result, atypical portable computer today can only play CDs for about 2–3 hours.

Operation of the Portable CD-ROM and Audio Subsection Today

Portable computers today are typically organized as a system including aMicroprocessor and its support chips, as well as common peripherals(including, e.g., the graphics subsection, PCMCIA controller, hard diskand floppy disk controller, interface port control for printer andserial busses, for example, keyboard controller, etc.) which interfaceto the CPU. A fixed disk drive and CD-ROM are typically attached on acommon bus, such as an IDE or SCSI bus. “ATAPI-compliant” CD-ROMs arecapable of either date retrieval, or playing audio disks (so called“Redbook” or “CD-A” disks). The CD-ROM control signals and data comeover the common bus, but audio signals are output directly from theCD-ROM on an independent analog output.

A typical example of a computer audio system employs an audio mixer or“SoundBlaster” compatible audio codec. The output of the CD-ROM is acommon input to the Audio Mixer. The function of the mixer is to providevolume control of the CD-ROM outputs along with other PC sounds. Theoutput of the mixer goes to a power amplifier, which outputs to speakersor to a headphone jack. The audio codec and power amplifier togetherform the Audio section of the computer.

A Real Time Clock (RTC) is a virtually universal peripheral to today'sPCs. The RTC is always powered up, and is used to both keep track of thetime and date and to act as an “alarm clock” to the system, whereby thesystem may be “woken” from Suspend after a predetermined time haspassed.

Power management circuitry is an integral part of a typicalbattery-powered computer. Power management is principally controlled bya program in the CPU memory and enables active status to the peripheralsand support logic of the system.

Typically, a low-power “Suspend” mode is supported, where the entirestate of the system is frozen, timing clocks are turned off, and poweris removed from any logic whose state is unimportant. Power to at leastsome portions of the system must remain active during Suspend. Thefunction of Suspend mode is to freeze the condition of the system whiletaking the least amount of power. In Suspend, the only activity thesystem supports is to recognize a “wakeup” event and return to normaloperation: the “RESUME” sequence may be initiated by the system (e.g. bybutton press, modem ring, Real time clock alarm, or low battery event).

Typical power dissipation for the unit in a FULL SUSPEND mode is about200 milliwatts. After “Resume” from Suspend, power to all devices isreturned, and the pre-existing states of the CPU, the operating system,and the application is restored to its state before Suspend wasexecuted.

Suspend mode is usually entered after a period of inactivity, after acritical condition event (for instance, a low battery condition orovertemperature of the unit), or manually by the user.

Typically, when in Suspend mode, power to the fixed disk and CD-ROMdrives are disconnected (shown here as SWI under the control of aSUSPEND status signal). The audio subsection is also placed into anon-functional mode; either power may be removed completely from thesystem or the Audio mixer/Codec and power amplifier may be placed into anon-functional SUSPEND mode under the control of the SUSPEND statusline.

The peripheral components are also placed into inactive functionality orturned off by the single SUSPEND status.

Applications run within the CPU to play an audio CD. For example, withinthe Windows operating system, these utilities are called “Media Player”or “CD player,” though many such applications are known.

Limitation of Known Implementations

For the sole purpose of playing an Audio CD, today's portable computeruses more power than is required. This is because, in order to play anAudio Compact Disk today, the entire peripheral set remains powered andfunctional, although they are not being used. Since a full SUSPENDglobally powers down all peripherals, it is not possible on today'sportable computers to allow the system to suspend all unnecessary systemelements while playing an audio CD.

Innovative System and Method for Low-Power CD Audio

The present application describes a computer system and method whichprovides a “CD-player Suspend” mode, where the audio section and CD-ROMare left active while the remaining system is placed into a low powermode.

BRIEF DESCRIPTION OF THE DRAWING

The disclosed inventions will be described with reference to theaccompanying drawings, which show important sample embodiments of theinvention and which are incorporated in the specification hereof byreference, wherein:

FIG. 1 shows a typical prior art computer system capable of entering asuspend mode; and

FIG. 2 is a computer system constructed according to the preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment (by way of example, and not of limitation), in which:Portable computers today are typically organized as shown in FIG. 1:

-   -   The “System” consists of a CPU 1; here, the CPU refers to the        Microprocessor and support chips themselves. The common        peripherals 8 (including, e.g., the graphics subsection, PCMCIA        controller, hard disk and floppy disk controller, interface port        control (printer and serial busses), keyboard controller, etc.)        interface to the CPU.    -   A fixed disk drive 2 and CD-ROM 3 are typically attached on a        common bus, in this case an IDE or SCSI bus. “ATAPI-compliant”        CD-ROMs are capable of either data retrieval, or playing audio        disks (so called “Red-book” or “CD-A” disks). The CD-ROM control        signals and data come over the IDE bus, but audio signals are        output directly from the CD-ROM on an independent analog output.    -   A typical example of a computer audio system employs an audio        mixer or “SoundBlaster” compatible audio codec 4. The output of        the CD-ROM is a common input to the Audio Mixer. The function of        the mixer is to provide volume control of the CD-ROM outputs        along with other PC sounds. The output of the mixer goes to a        power amplifier 5. Final output of the power amp is to speakers        or to a headphone jack. The audio codec and power amplifier        together comprise the Audio section of the computer.    -   A Real Time Clock (RTC) 6 is a universal peripheral to the PC.        The RTC is always powered up, and is used to both keep track of        the time and date and to act as an “alarm clock” to the system,        whereby the system will be “woken” from Suspend after a        predetermined time has passed.    -   Power management circuitry 7 is an integral part of the        battery-powered computer. Power management is principally        controlled by a program in the CPU memory and enables active        status to the peripherals and support logic of the System.

This application describes a method and system for enabling a low powerAudio CD player mode, where the CPU is put into Suspend and the Audio CDis allowed to play. Without this mode, a typical portable computer couldonly play CDs for about 2–3 hours; with this mode, performance of 10–15hours on a battery charge is possible. The convenience is for mobileusers who want to enjoy the performance of a standalone “Diskman” butdon't want the carry weight and size of a separate player.

The basic operation for the presently preferred embodiment is tointerrogate the status of the CD-ROM when a Suspend is initiated, anddecide which of two low power states to configure the CD-ROM drive andthe audio subsection to. The preferred embodiments include a system andmethod to separate “global” Suspend (whereby all peripherals are turnedoff) from the “CD-player” Suspend.

-   -   A. The hardware required for the presently preferred embodiment        is not altogether unique but requires a certain minimum of        functionality;        -   i. As with the traditional portable, the processor and            peripheral set (graphics subsystem, processor and supporting            chipset, keyboard controller, peripheral controller, etc)            can be placed into a low-power SUSPEND mode.        -   ii. One important feature of the preferred embodiment is the            ability to leave the Audio mixer portion of the Codec and            the power amplifiers in an active state independent of the            state of the peripherals or processor. In this state the            output of the CD-ROM audio channel may be output through the            codec and amplifiers.        -   iii. Another important feature of this embodiment is the            ability to leave the CD-ROM active when playing an audio CD,            independent of the Suspend status of the peripherals and            processor.        -   iv. Another feature of this embodiment is the ability to            remove power from the Fixed disk while leaving power to the            CD-ROM (allowing the CD-ROM to remain active). There are            several standard ways (and one unique way) to accomplish            this. In one alternative, the Fixed disk drive may be placed            into a low power Suspend condition independent of the            CD-ROM.        -   v. Optionally, a signalling method for Audio CD commands            (for example, fast forward, seek, skip) from the keyboard or            control panel may become active when the unit is in a “CD            Player Suspend” mode.    -   B. Logic is called during the system entrance into Suspend. The        purpose of this logic is to;        -   i. Interrogate the system to find if an audio CD is playing            in the CD-ROM drive. This interrogation may be manual or            automatic.        -   ii. As with traditional portables, configure the processor            and all peripherals to lowest power mode (“Full Suspend”) if            no audio disk is playing in the CD-ROM.        -   iii. (Unique to this invention) to configure the processor            and peripherals to lowest power mode while allowing the            CD-ROM drive and Audio subsection to remain active if an            Audio CD disk is playing.    -   C. One feature of the preferred embodiment is a method to exit        the low power “CD-player Suspend” once the audio CD is finished        playing and configure the machine to an Active state, to a “Full        Suspend” state, or to an “Off” state.    -   A. Specific Hardware Implementation

FIG. 2 shows a specific Hardware implementation of the low power CDplayer.

-   -   11. Section 11 comprises the CPU and its support chips. In this        instance, the processor is a Pentium CPU and the support chips        are the Opti 558 family (556, 557, 558, and 602 devices). A        general purpose output of the 602 chip is set high by the CPU        when a SUSPEND operation is to occur. Another general purpose        output controls the new function, AUDIO_SUSPEND. Both outputs        are under control of the CPU via writes to I/O register        locations across the ISA bus.    -   12. The Fixed Disk drive 12 is connected to the IDE bus. The        power to the fixed disk drive is enabled through a transistor        which is turned OFF when Suspend is active. This switch is        represented at SW1.    -   13. The CD-ROM 13 has separate power control, enabled through        SW3. SW3 is a transistor which is turned off when the signal        AUDIO_SUSPEND from section 11 is active.    -   14. The audio mixer and codec functions are performed with an        ESS1688 device 14. The ESS1688 is a single-chip        SoundBlaster-compatible device which interfaces to the CPU        across an ISA bus. The ESS1688 device may be placed into        “partial standby,” where the digital section (the Codec function        of the ESS) is placed into suspend but the analog mixer section        remains active. This enables the ESS device to continue to        function as a volume control when the System is in CD-player        Suspend mode. The ESS1688 device is placed into a partial        standby mode by writes across the ISA bus to registers inside        the device. Power is applied to the ESS1688 device during both        SUSPEND or CD-Player Suspend modes. The specification for the        ESS1688 may be obtained from ESS Technology, Inc., 48107 Landing        Parkway, Fremont, Calif. 94538-6407, U.S.A., and is hereby        incorporated by reference.    -   15. Power to the audio amplifiers 15 is enabled through a        transistor gated by AUDIO_SUSPEND.    -   16. The Real Time Clock 16 (RTC) function is performed by the        602 chip. The RTC functions are always active. In this specific        implementation, the RTC is used to terminate the CD-player mode        by waking the system after the audio CD will have finished        playing.    -   17. Power management circuitry 17 is an integral part of the        battery-powered computer. Power management is principally        controlled by a program in the CPU memory and enables active        status to the peripherals and support logic of the System.    -   18. The peripheral chips 18 (the graphics controller, fixed disk        drive logic, parallel and serial port controls, etc) is powered        off by disabling a transistor connected to VCC. (In usual        practice, the register contents of these peripherals will be        read and stored into non-volatile memory under control by the        CPU before power is removed). The transistor is turned off when        the signal SUSPEND is active.    -   19. Because the CD-ROM drive 13 shares the IDE bus with the        Fixed disk drive 12, and power is removed from the Fixed disk        drive, the control lines attached to the IDE device will go low.        Since the CD-ROM control lines are active low, this would force        the CD-ROM into an active state and upset the state of the        CD-ROM. To avoid this, the control lines to the CD-ROM must be        forced into a non-active state. In the preferred embodiment,        this function is performed by isolating the control lines to the        CD-ROM with a tristatable buffer 19 gated by AUDIO_SUSPEND. The        lines which are tristated include the RESET*, WRITE*, and READ*.        The CD-ROM control lines are held inactive through the use of        pullup resistors added between the CD-ROM inputs and VCC.

B. A Method to Enter and Exit CD-Player Mode

This process is performed when a SUSPEND is requested. According to thepreferred method; the system interrogates whether the CD-ROM is playingan Audio-CD and determines the appropriate power state of the system.The system then enables a mechanism for terminating the CD-Playersuspend mode and returns the system to a Full Suspend mode. As is usualfor any SUSPEND function, the software for performing these functions isstored in BIOS ROM accessible by the CPU.

1. Interrogating the CD-ROM

Characteristic of an ATAPI compliant CD-ROM is the command “Play AudioCD.” This command will be issued by an application, for example the“Media Player” application under the Windows operating system. Afterthis command is issued, the CD-ROM will play without any furtherinstruction by the CPU.

In the preferred embodiment, the system determines if the CD-ROM isplaying an Audio CD through an ATAPI query to the CD-ROM drive.Available, standard ATAPI commands include the REQUEST SENSE, INQUIRE,and READ CD commands. The CD-ROM will respond with a status byteindicating if an Audio CD is busy playing.

2. No Audio CD is Playing

If no audio CD is playing (an ATAPI query answer replies negatively)then the entire system is placed into Full SUSPEND. The system performsnormal SUSPEND function (copies all important register data tonon-volatile memory and enables a Resume event) before concluding withthe below power sequence;

-   -   a. The ESS1688 is put into Full Suspend. Full suspend is entered        by setting bit 3 of the Power management register (register 227        h) to a “0” (“ANA-LOG stays off”); then by pulsing bit 2 high,        then low.    -   b. Power to the CD-ROM and to the power Amplifiers is turned off        by setting the line AUDIO_SUSPEND active.    -   C. Power is removed from the remaining chipset (and main        functional clocks are terminated) by setting the SUSPEND line        active.        3. An Audio CD is Playing

If an Audio CD is playing (ATAPI query returns “Playing Audio CD”status) then the CD-ROM drive and Audio are left active while the restof the system is placed into Suspend.

After copying the state of the peripheral set registers to non-volatilememory (the normal operation before executing a full Suspend) the systemperforms the following timing sequence;

-   -   a. The ESS1688 is placed into “partial suspend.” Partial suspend        is entered by setting bit 3 of the Power control register to a        “1,” then by pulsing bit 2 high, then low.    -   b. Power to the CD-ROM is left to the CD-ROM, and to the power        amplifiers by leaving the signal “CD-player Suspend” line        inactive.    -   c. A mechanism is employed to terminate the CD-player mode and        return to the Full Suspend mode when the CD is through playing.        This mechanism uses the RTC device to periodically wake the        System from “CD-player Suspend” to “Full awake” condition. This        is accomplished by;        -   i. the RTC has an alarm feature. When the actual time            matches a preset time, an “alarm” is issued. The alarm is            activated by reading the present time, adding a certain            amount to the time, then writing to the Alarm register            inside the RTC. In this example, 15 minutes is added to the            actual time to create the Alarm time (the alarm will ring 15            minutes later). The alarm registers are indexes 01 h, 03 h,            and 05 h inside the RTC I/O location of 70 h and 71 h.        -   ii. The alarm is enabled to wakeup the System by setting the            IRQ *in this case, ISA IRQ8 from the RTC) to generate a            “RESUME” event. This is done by writing to the register            SYSCFG 6Ah, bit 6 inside the 602 chip.    -   d. The system enters an otherwise “full” suspend by setting the        Suspend line active. The CPU (1), peripheral set (8), and hard        drive (2) will become inactive and the isolation to the CD-ROM        (9) will become active. The state of the CD-ROM is thus        preserved, and the power amplifiers will continue to operate in        the “CD-Player” suspend mode.    -   e. A mechanism checks to see if the Audio CD is finished        playing. 15 minutes after the System enters CD-player suspend        mode, the RTC will issue an IRQ and the system will RESUME.        Normally upon a resume, a full restoration is made to the system        and the peripheral set. For the preferred embodiment, a limited        RESUME occurs, where the only task for the processor is to query        the CD-ROM for playing status and the system repeats the entire        process (at 1 above) If the CD-ROM has stopped playing the audio        CD, a query to the CD-drive will return the status “Audio disk        stopped.” In that case (no audio CD is playing) the system will        enter at “2” and issue a full Suspend. If the Audio CD is        playing, the system continues at “3” and the Audio CD continues        playing.

According to one disclosed embodiment, there is provided a method foroperating a portable computer system, comprising the steps of: receivinga command to place said system in a suspend mode; determining whether anaudio CD is playing in a CDROM drive; if an audio CD is not playing,placing said system in a suspend mode; if an audio CD is playing,continuing to operate said CDROM drive, while placing the remainder ofsaid system in a suspend mode.

According to another disclosed embodiment, there is provided a methodfor operating a portable computer system, comprising the steps of:receiving a command to place said system in a suspend mode; determiningwhether an audio CD is playing in a CDROM drive; if an audio CD isplaying, then leaving said CDROM drive in its present state; isolatingat least one of a plurality of CDROM control signals from other systemsignals; placing a digital section of an audio CODEC in a suspend mode;leaving an analog section of said audio CODEC in an active mode; andleaving at least one audio power amplifier in an active state; if anaudio CD is not playing, then placing said CDROM drive in a suspendmode; placing said audio and digital sections of said CODEC in a suspendmode; placing said audio power amplifier in a suspend mode.

According to another disclosed embodiment, there is provided a portablecomputer system comprising: a microprocessor; a memory connected to saidmicroprocessor; a display device connected to display data generated bysaid microprocessor; an audio controller connected to saidmicroprocessor; an audio input device connected to said audio controllerfor reading audio data; a battery connected to power saidmicroprocessor, memory, display device, audio controller, and audioinput device; wherein said system may be placed in a suspend mode inwhich said microprocessor and display are placed reduced power state;and wherein said audio input device and said audio controller may beselectably placed in a reduced power state when said system is in saidsuspend mode.

FURTHER MODIFICATIONS AND VARIATIONS

As will be recognized by those skilled in the art, the innovativeconcepts described in the present application can be modified and variedover a tremendous range of applications, and accordingly the scope ofpatented subject matter is not limited by any of the specific exemplaryteachings given.

Variations of the CD-ROM Isolation Logic 9

The preferred approach isolates the CD-ROM from the IDE bus when the lowpower CD-Player suspend mode is enabled. There are other methods foraccomplishing this;

-   -   1. No isolation is used between the Fixed disk drive and the        CD-ROM. There are 2 variations of this method;        -   a. The hard drive and CD-rom drive may be powered at the            same time; no effort is made to isolate the CD-rom power            from the hard drive power. The fixed disk may be placed in            to a SUSPEND mode by writing to a control register in the            Fixed disk itself. Because the Fixed Disk drive is powered            up in this mode, it will not activate the (active low)            control signals on its attached IDE bus as it would if            powered off. This is not the preferred approach, since today            the fixed disk drive consumes about half a watt when in            SUSPEND (about 20% of the CD-Player suspend power budget).        -   b. The hard drive logic may be “input tolerant” so that when            the hard drive is unpowered, there is no conduction between            the IDE bus and the hard drive. No such drives exist today.    -   2. Isolation may be used on the hard drive; instead of        decoupling the IDE bus from the CD-rom drive during CD-Player        mode, the hard drive may be decoupled and powered off. This        requires the IDE interface logic to maintain an inactive state        during the CD-Player Suspend.    -   3. Isolation may consist of a latch instead of a tristatable        buffer (section 9) since the purpose of the isolation is simply        to maintain the present state of the CD-ROM.    -   4. The CD-ROM may remain powered during either Full SUSPEND or        CD-PLAYER SUSPEND, but have the CD-ROM enter a low-power Suspend        condition instead of being powered off when no audio CD is        playing.

Variations in the Audio Mixer

The audio mixer could be bypassed completely in CD-Player mode. Volumecontrol could be done by other passive or active circuitry. In thepreferred approach, volume control is performed simply with apotentiometer located between the Audio Mixer and the power amplifier.

Variations in Termination of CD-Player mode

The preferred approach uses the RTC to wakeup the system periodicallyand re-evaluate the status of the CD-ROM. Other approaches may be used;

-   -   1. The RTC may be set for a single maximum time before the        CD-Player mode is exited. The time may be the maximum possible        length of an audio CD (74 minutes) or the system may determine        the playing time remaining on the present CD and set the RTC        alarm for that length of time.    -   2. The System could wake up upon an opening of the CD-drive        tray. This would be more convenient to a user who wants to start        playing another disk, since the application to initiate playing        of the next CD would be available through the operating system.        One possible implementation for this is to have the IRQ on the        IDE bus wake the system from CD-PLAYER SUSPEND to Fully active,        where the application which initiates the CD-player function        could restart.    -   3. The CD-Rom drive could accept commands from another control        source when in CD-Player suspend for common Disk player commands        such as track skip, fast forward reverse, etc. In this        variation, control buttons which are read by the System during        Fully On operation but are read by the CD-ROM when in CD-Player        mode. A possible implementation for this is;        -   1. On the system enclosure are dedicated lines for the            CD-rom commands. During normal (fully ON) operation, these            lines are read by the keyboard controller and instruct an            audio disk player application running under the operating            system. The Application itself instructs the CD_ROM to            change tracks, etc by issuing ATAPI packet commands to the            CD-ROM.        -   2. During CD-Player mode, the buttons are read directly by            the CD-ROM with no required intervention by the CPU. A            possible implementation of this is to change the function of            the IDE bus to signal the CD-ROM drive that the CD-Player            mode is engaged, and to signal directly to the CD-ROM (not            through the packet ATAPI commands) entrance to CD-player            mode, the CD is alerted to use the alternative control lines            instead of ATAPI commands.

Variation on the Method

The preferred approach interrogates the ATAPI CD-ROM by query commandsto detect the playing status of the CD. Other methods exist to determineif a CD is playing an Audio Disk;

-   -   1. Another method for determining if an audio CD is playing is        for the application which initiates the CD-rom playing the Audio        disk to “register” with the system when a play is initiated.        Instead of the system reading the state of the CD-ROM drive, it        can instead read simply a memory bit which is set by the        application itself.    -   2. The system can monitor the audio output stream of the audio        mixer to determine if a CD-ROM is active. In this        implementation, the system would measure the analog output of        the CD-ROM to determine the status of the CD-ROM drive. The        system could also use this to detect when an Audio CD is        finished playing and terminate the CD-Player mode.    -   3. An activity line from the CD-ROM itself could indicate that        the CD-ROM is busy playing an audio CD. A possible        implementation is for the Audio CD-rom to hold its DASP* line,        Interrupt line, or Activity LED active during Audio CD play. The        DASP* line is commonly used to indicate data read activity from        a CD-ROM drive, but usually does not become active today during        play of an Audio CD. So such an implementation would require an        enhancement of the current ATAPI CD-ROM drive.

It should also be noted that the disclosed innovative ideas are notlimited only to Windows, DOS or UNIX systems, but can also beimplemented in other operating systems.

It should also be noted that the disclosed innovative ideas are notlimited only to systems using ISA, EISA, and/or PCI busses, but can alsobe implemented in systems using other bus architectures.

It should also be noted that the disclosed innovative ideas are notlimited only to systems based on an x86-compatible microprocessor, butcan also be implemented in systems using 680'0, RISC, or other processorarchitectures.

It should also be noted that the disclosed innovative ideas are not byany means limited to systems using a single-processor CPU, but can alsobe implemented in computers using multiprocessor architectures.

1. An apparatus, comprising: isolation logic configured to isolate acomputer system from a CD-ROM drive; and control logic configured tocouple to the CD-ROM drive, the control logic capable of placing theCD-ROM drive into a plurality of power states; wherein the control logicplaces the CD-ROM drive into a full-power state to thereby cause theisolation logic to isolate the computer system from the CD-ROM drive,and cause the CD-ROM drive to be operational for playing an audio CDwhile the computer is in a reduced-power state.
 2. The apparatus ofclaim 1, wherein the reduced-power state comprises an off state.
 3. Theapparatus of claim 1, wherein the control logic enables the CD-ROM driveto receive user inputs from control buttons while the computer is in thereduced-power state.
 4. The apparatus of claim 1, wherein the controllogic is further configured to couple to an audio amplifier that iscoupled to the CD-ROM drive, and wherein the control logic is configuredto place the audio amplifier into the same power state as the CD-ROMdrive.
 5. The apparatus of claim 4, wherein the CD-ROM drive accepts theaudio CD, and audio extracted from the audio CD is provided to the audioamplifier while the computer is in the reduced-power state.
 6. Theapparatus of claim 5, wherein the control logic places the audioamplifier into the reduced-power state when the CD-ROM drive is nolonger playing the audio CD.
 7. The apparatus of claim 1, wherein thecontrol logic places the CD-ROM drive into the reduced-power state whenthe CD-ROM drive is no longer playing the audio CD.
 8. An apparatus,comprising: control logic configured to couple to a CD-ROM drive and acomputer, and further configured to select a control source thatreceives user input; wherein the user input causes the control logic toset the CD-ROM drive to a full-power mode if the computer is not in thefull-power mode; and wherein the CD-ROM drive plays an audio CD inresponse to the user input while the computer is not in the full-powermode.
 9. The apparatus of claim 8, wherein control buttons are selectedas the control source if the computer is not in the full-power mode. 10.The apparatus of claim 8, wherein an audio disk player applicationprogram executing on the computer is selected as the control source ifthe computer is in a full-power mode.
 11. The apparatus of claim 8,wherein the control logic sets the CD-ROM drive to a reduced-power modewhen the CD-ROM drive has stopped playing the audio CD.
 12. Theapparatus of claim 11, wherein the reduced-power mode comprises turningoff the CD-ROM drive.
 13. The apparatus of claim 8, wherein the controllogic is further configured to couple to an audio amplifier coupled tothe CD-ROM drive and to set the audio amplifier to the same power modeas the CD-ROM drive.
 14. The apparatus of claim 13, wherein audioinformation read from the played audio CD is provided to the audioamplifier while the computer is not in the full-power mode.
 15. Theapparatus of claim 14, wherein the control logic sets the CD-ROM driveto a reduced-power mode when the CD-ROM drive has stopped playing theaudio CD.
 16. The apparatus of claim 15, wherein the reduced-power modecomprises turning off the CD-ROM drive.
 17. The apparatus of claim 14,wherein the control logic sets the audio amplifier to a reduced-powermode when the CD-ROM drive has stopped playing the audio CD.
 18. Theapparatus of claim 17, wherein the reduced-power mode comprises turningoff the audio amplifier.